U.S. lawmakers return to Washington next month and they face a deadline of October 1 on how to continue funding the federal government.

A group of Republicans is threatening to force a government shutdown unless Congress votes to deny funding for President Barack Obama’s signature health care reform law, known as the Affordable Care Act.

Obama signed health care reform into law in 2010, but the battle over its implementation continues. Groups for and against the health-care law are running TV ads in hopes of winning public support.

Some Republicans are demanding that Congress defund the health care law as part of any agreement to renew overall government spending in October, including Texas Senator Ted Cruz.

“It is not working, said Cruz. "It is hurting health care and now is the opportunity to do it if the American people rise up and hold our elected officials accountable.”

Joining Cruz in the effort is Florida Senator Marco Rubio, both are considered potential presidential contenders in 2016.

“It will do irreparable damage to our economy and to our country," said Rubio. "I do not think you can say that you are against Obamacare if you vote for a budget that funds it.”

The Republican-controlled House of Representatives has frequently voted to defund the health-care law.

But the effort has been blocked in the Democratically-controlled Senate and would be vetoed by the president.

Obama was asked about the defunding effort during a recent news conference. He said, “The idea that you would shut down the government unless you prevent 30-million people from getting health care is a bad idea.”

Congressional Democrats are also fighting the idea of defunding the law, including House Democratic leader Nancy Pelosi.

“I think they are aimless," she said. "I think they are chaotic and I think they are making matters worse for the American people when we should be resolving this.”

A number of senior Republicans in both the House and Senate also oppose the effort to defund and the issue has become a point of division within the party. But Republican congressional leaders, including House Speaker John Boehner, remain noncommittal.

“And I am confident that when we get into the fall we will find that it may be a messy process, but I suspect we will find a way to get there,” he said.

The move to defund Obamacare is being driven by Tea Party activists, says analyst David Hawkings of Roll Call, a newspaper that covers Congress.

“Conservative Republicans, the Tea Party Republicans have been itching for a fight ever since they got here in 2011. ... There are still a solid number of Republicans in the House especially who are itching for that kind of a confrontation and think they will win it,” he said.

Republican strategist Ford O’Connell is among those warning Republicans not to do it.

“It is a very, very risky strategy that could come back and bite the Republicans at a very important time when they are trying to change their identity and change their perception and win elections in 2014, so they can grow their numbers and govern in Congress,” he said.

Veteran Republicans worry that because they were blamed for government shutdowns in the 1990’s during budget confrontations with former President Bill Clinton they will be again if there is a shutdown over the health-care law.

Jim Malone has served as VOA’s National correspondent covering U.S. elections and politics since 1995. Prior to that he was a VOA congressional correspondent and served as VOA’s East Africa Correspondent from 1986 to 1990. Jim began his VOA career with the English to Africa Service in 1983.